• Outlook cannot read the calendar


    Yesterday Outlook (Microsoft 365 home premium) was working fine.  Today when I opened Outlook, it said “cannot read the calendar,” even though it actually could, as I determined by looking through the calendar.  Opening Outlook with the /safe parameter did not get the error initially but clicking on the Calendar icon results in the error, even though the calendar can actually be read as before.  The only add-ons installed are Microsoft’s own.  Also, near as I can tell, there were neither Office nor Windows updates applied over night.  The data file is not the culprit because it opens just fine when copied to my laptop and opened with Outlook there.  I uninstalled Microsoft 365 with the Microsoft Support and Recovery Assistant, then re-booted and re-installed Microsoft 365.  The first time I opened Outlook, the error did not recur, but it recurred on every subsequent time.  I’m baffled and at loss to know what to try next.

    Viewing 11 reply threads
    • #2355958

      Try CalCheck?

      CalCheck is a program that checks your Outlook calendar for problems, and performs various checks on general settings, such as permissions, free/busy publishing, delegate configuration, and automatic booking. Then, each item in your calendar folder is checked for known problems that can cause unexpected behavior, such as meetings that seem to be missing.

      Resolve Outlook for Windows issues with automated troubleshooting tools

      • #2355975

        I wouldn’t expect CalCheck to fix the problem because (1) there is no error if I move the PST file to my laptop and open with Outlook there and (2) even on my desktop, after the error shows, Outlook displays the calendar just fine.

    • #2355960

      You mentioned using Microsoft Support and Recovery Assistant to remove Office 365.

      Did you also use that tool to fix Outlook problems, “I’m having problems with my calendar”?

      • #2355974

        No, just to re-install Office.  First opening of Outlook was fine.  Subsequent openings got the “cannot read calendar” error again.  So far, not fixed.

    • #2356262

      After banging my head against the wall, trying various things, I decided AskWoody MVP “B” undoubtedly knows a lot more than I do, so I decided to try CalCheck.  I’m getting an error message that is Greek to me:

      ERROR: , Code: 0x8004010F, Function OpenMessageStoreGUID(lpMAPISession, pbExchangeProviderPrimaryUserGuid, &lpMDB), File CalCheck.cpp, Line 470
      ERROR: Could not connect. Ensure you are connecting Outlook via MAPI to an Exchange server.

      I don’t have an Exchange server, just Office locally installed.  B, can you give me a clue what I”m doing wrong.  TIA

    • #2356534

      I have the same problem.  Outlook (Office 365) JUST DID AN UPDATE!!

      Update 16.0.13901.20336

      I am very sure this is the problem.

      I tested this buy creating a new PST file and copied the exported calendar to the new PST and the SAME error happens.

      Poor quality on MSFT’s part!

    • #2357573

      Also reporting this issue, seen after a Monday update, on 13901.20400 currently. Have two users with this so far, worried we may see more soon.

      Not much troubleshooting yet, only tried Safe Mode and no effect on the issue. To-Do Bar Calendar on the right side curiously will keep the most recently added single calendar item listed and all recurring items. Any other one-off events are unlisted.

      • #2357599

        Got any third party plug ins or something holding on to the pst file?  These are all pst’s correct?  Are they shared out from an unusual location?

        Susan Bradley Patch Lady/Prudent patcher

        • #2357629

          No PSTs, we block them because it fills up OneDrive storage typically. Set for Exchange with cached mode enabled.

          We have a few add-ins like Mimecast, but I was under the impression Safe Mode disables add-ins and is a quick way to determine if they are the fault or not.

          We may have been able to fix the issue. Doing a profile recreation and letting Exchange pull everything again fresh has removed the error & calendar items on sidebar are showing correctly again. If we reboot or anything and the issue comes back, will post again to alert.

    • #2357780

      I’m having exactly the same problem. I click on ‘couldn’t read calendar’ and i then can see add/delete items to the calendar. I’m fed up with having to click ‘OK’ in the box.

    • #2357801

      Have you tried to test your PST file with the tool, that is part of the installation of Office?
      Its called SCANPST.EXE and it can repair “broken” PST files. It helped me lot of times. Simply select your actual PST file and scan it. It can take an hour, depending on your file size.

      Im not sure, if you recreated your account from scratch, or you just keep copying the old one..

      I tested this buy creating a new PST file and copied the exported calendar to the new PST and the SAME error happens.

      But try the SCANPST.EXE first. Its worth trying.

      But profile recreation is the best way by my opinion!

      We may have been able to fix the issue. Doing a profile recreation and letting Exchange pull everything again fresh has removed the error & calendar items on sidebar are showing correctly again. If we reboot or anything and the issue comes back, will post again to alert.


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    • #2358171

      I am having the exact same problem.  As there is no apparent fix at this point, I just try imagining the message doesn’t say “cannot read the calendar” but instead says “good morning”, “good afternoon” or “good evening” depending on the time of day.  I’m hopeful a solution will be discovered soon.

    • #2358633

      There are many complaints about “Could not read the calendar” in Microsoft 365 Outlook at Microsoft “Answers” over the last six weeks:

      Microsoft Outlook Error: Could not read the calendar

      Outlook error message – “can not read calendar”

      Outlook “Could not read the calendar” pop-up April 2021 after Office 365 Update 16.0.13901.20336

      Could not read the calendar message

      The best information was published in a Slipstick.com newsletter a few days ago:

      Could not read the calendar

      Several users are reporting a calendar error: “Could not read the calendar“ when they switch to the Calendar or to the Inbox. The appointments display properly and the usual fix for this error – reset the view – does not fix the problem.

      Turning off the To-Do bar calendar reduces the number of times the error dialog comes up. Keeping the calendar open in a separate window so you don’t need to keep switching between the Inbox and Calendar will also reduce the number of times you see the error message.

      Microsoft is investigating this. In the meantime, if you are affected by this bug and the error is too annoying, you can roll back to an older version of Office.

      To rollback, type cmd on the start menu, right click on the Command Prompt, choose Run as Administrator then copy and paste the line in the command prompt. (This is a March 30 2021 build)

      “C:Program FilesCommon Filesmicrosoft sharedClickToRunofficec2rclient.exe” /update user updatetoversion=16.0.13901.20312

      I have more information on rolling back Office installs and the complete command to use at Uninstall Updates in Office ‘Click to Run’ (slipstick.com)

      Exchange Messaging Outlook – April 15 2021 – Volume 26 Issue 10
      A weekly newsletter about Microsoft Exchange and Microsoft Outlook
      by Diane Poremsky, Outlook expert and Microsoft MVP

      I’m not yet convinced that rolls back far enough. If I was going to revert to an earlier version to avoid the error message I would use version 16.0.13801.20294 from March 9, 2021.

      • This reply was modified 2 years, 10 months ago by b. Reason: Corrected date on last line from March 1 to March 9
    • #2359007

      My apologies for not responding sooner to all the good folks who were trying to help.  I was doing a bunch of testing with a copy of my PST file and getting nowhere.  The solution for me was indeed to roll back my Office version.  I tried the 16.0.13901.20312 version first, but the error persisted.  Then I rolled back to 16.0.13801.20294, and poof, the error vanished.  Thank you very much for that suggestion and describing how accomplish the rollback.

      1 user thanked author for this post.
    • #2359159

      I was experiencing this same problem, as others have described.  My machine updated last night, and today this problem is resolved.  Hope this helps others.
      • #2359163

        The build number which fixed it would help a lot more.

        (File, Office Account, About Outlook.)

        • #2359169

          Sorry, Windows 10 build version: 19042.928 with Windows Feature Experience Pack 120.2212.551.0

          Outlook version 2103 (Build 13901.20400) Current Channel.


          1 user thanked author for this post.
    • #2359890

      Diane Poremsky, who provided details above, now confirms that latest updates are fixed:

      Fixed: Could not read the Calendar

      Last week I mentioned an error some users experienced when they switched between the Mail and Calendar modules, receiving a message “Could not read the Calendar”.

      This bug is fixed. If you were affected by this bug and still have it, check for updates in Outlook then restart it. The fix is installed when you restart Outlook.

      Exchange Messaging Outlook – April 22 2021 – Volume 26 Issue 11

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